Throughout the arts, there are many instances where it is required that liquids must be chilled and where chilling the liquids is effected by the transfer of heat between the liquids and prechilled fluid coolants. To effect such transfer of heat, the fluids and coolants are conducted through heat exchange structures including adjacent fluid and coolant-conducting means that separately handle the fluids and coolants and through which heat is transferred from the liquids to the coolants.
Typically, the liquid to be chilled is water or a beverage or other acquiesce solution. The prechilled coolant can be water, an antifreeze solution such as glycol; or, a refrigerant such as freon.
For the purpose of this disclosure, the fluid to be chilled is potable water received from a common pressurized water supply system and that is chilled for serving and/or for the making and serving of chilled beverages, such as lemonade.
The most common and widely used prior art water chillers provided to dispense chilled potable water for drinking or making and serving chilled beverages, such as lemonade, are called ice bank chillers. Those chillers consist of unsealed tanks filled with volumes of heat transfer water. Elongate stainless steel water-conducting coils, through which potable water to be chilled is conducted, are arranged within the outer perimeters of the tanks and are immersed in the heat transfer water. Elongate refrigerant expansion coils are arranged centrally in the tanks in inward spaced relationship from the water coils. The refrigerant expansion coils are parts of common refrigeration machines that are parts of the water chillers. The coolants (freon refrigerant) are conducted through the expansion coils and freeze the heat transfer water about the coils to create banks of ice in the central portions of the tanks. The banks of ice chill the remainder of the heat transfer water in the tanks, in which the water coils are immersed. The chilled heat transfer water absorbs heat from the potable water flowing through the water coils.
Ice bank chillers of the character referred to above are, from the standpoint of size, weight and power consumption, extremely inefficient. As the volumetric demand for chilled water increases, the size, weight and power consumption of ice bank chillers increase at an exponential rate.
In most instances, space that is available to accommodate ice bank chillers is costly or expensive space and is, with few exceptions, quite limited. As a result of the foregoing, there are many instances where the demands for chilled water cannot be met with ice bank chillers.
Another serious shortcoming of ice bank chillers resides in the fact that the rates of flow of potable water therethrough must be carefully monitored to assure that the volumes of warm inflowing water do not result in rapid melting away of the ice banks, since as the ice banks melt away or down, the efficiency of the chillers to chill the water is reduced at an exponential rate. Further, when the ice banks are melted down to an extent that the potable water is not suitable chilled, the chillers must be put out of service a sufficient period of time to allow the ice banks to grow to full and efficient size. Since the ice banks are created by refrigerants flowing through the expansion coils deep within the ice banks, growing of new ice at the exterior of the ice banks is an extremely slow process that often takes many hours.
In furtherance of the above, it is to be noted that when ice bank chillers are put into service, they must be let to run idle for several hours to allow effective ice banks to be built and before chilled potable water can be drawn therefrom. This is a serious shortcoming since it requires along initial "chill-down time" prior to putting the chillers to their intended use.
In addition to the above-noted ice bank chillers, the prior art provides more sophisticated, complicated and notably more costly chillers for chilling water. One such chiller consists of a tank containing a supply of potable water, a metal canister within the water in the tank and an expansion coil of a refrigeration machine within the canister. The metal canister absorbs heat from water in the tank and conducts it to the coil within the canister. The refrigerant conducted through the coil absorbs and carries away the heat.
Another common form of heat exchangers that are widely used to chill water and beverages consists of cold plates of cast aluminum within which coolant and water-conducting coils are arranged. Coolants, chilled by suitable coolant-chilling means, such as ice bank chillers, are conducted through the coolant coils in the plates to carry heat out and away from the plates. The chilled plates absorb heat from the water flowing through the water coils in the plates. The cold stored by the plates make these heat exchangers quite effective and efficient. The size of these exchangers is quite small, with respect to their capacity to chill water, and are such that they can be conveniently accommodated in spaces where other water-chilling means, such as ice bank chillers, cannot be accommodated. Cold plate chillers must be used in combination with other water chiller means that supply them with the required coolants.
To the best of our knowledge and belief, all of those prior art heat exchanger means suitable for chilling water or the like, in which a prechilled coolant is used to chill a liquid, such as water, make poor and inefficient use of the prechilled coolants and, with possible exceptions, tend to be excessively large, heavy and costly to make, operate and maintain.